Measurement of the ⁶Li(n,α) neutron standard cross-section at the GELINA facility

¹ Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
² European Spallation Source, Box 176, 221 00 Lund, Sweden
³ European Commission, Joint Research Centre, Institute of Reference Materials and Measurements (IRMM), Retieseweg 111-2440 Geel, Belgium

^a e-mail: kaj.jansson@physics.uu.se

Published online: 21 June 2016

Abstract

The ⁶Li(n,α) reaction cross-section is commonly used as a reference cross section. However, it is only considered a neutron standard up to 1MeV. For higher energies, there are discrepancies of several per cents between recent measurements and evaluated data files. In order to extend and establish ⁶Li(n,α) as a neutron standard above 1MeV these discrepancies must be resolved.

Our measurement at the GELINA facility at JRC-IRMM in Geel, Belgium is ongoing. We are using a double twin Frisch-grid setup to detect both α-particles from two ⁶Li targets and fission products from two ²³⁵U reference targets. Our targets have thick backings but are employed in pairs, one forward facing and one backward facing. In this way we still cover, in principle, a solid angle of 4π. We present some preliminary results showing that the existing cross-section data is well reproduced around the resonance at 240 keV. The final data taking will start in the beginning of 2016, when the GELINA facility goes online again after a few months of shut down.